1. Field of the Invention
The invention relates to a method of manufacturing ultra-pure sulfuric acid, specifically relates to a continuous manufacture method of ultra-pure sulfuric acid which is in conformity with SEMI C12 standard for cleaning and etching the wafer during the manufacturing process of semiconductor component.
2. Description of the Related Art
Ultra-pure sulfuric acid, also known as electronic grade sulfuric acid, is a very important kind of microelectronics chemical reagents. With the rapid development of electronic industry, the consumption of ultra-pure sulfuric acid in the semiconductor industry accounted for about 30% of total ultra-pure reagents. It's widely used in semiconductors, ultra-large scale integrated circuit assembly and processing. The purity of ultra-pure sulfuric acid has a significant impact on the yield of cleaning, etching products, electrical performance and reliability, for example the ultra-pure sulfuric acid can effectively remove the impurity particles, inorganic residue and carbon deposits on the wafer while cleaning, etching. Generally, the purity of ultra-pure sulfuric acid is required to meet to the chemical materials level 12, SEMI C12 standard formulated by Semiconductor Equipment and Materials International (referred to as SEMI C12 standard), the mass fraction of metal impurity level should be less than 0.1 ppb (1×10−10 to 1×10−11).
Among the existing technology, the traditional method is to direct distill the industrial sulfuric acid to remove impurities with high boiling point to obtain sulfuric acid with high purity. The product manufactured by this method contains impurities which is hard to be removed by distillation, the content of impurities is not conformity with SEMI C12 standard, since the boiling point of the sulfuric acid reaches a high temperature 330° C., therefore the energy consumption during the distillation and the cost are high, the waste gas and the acid mist generated during the distillation will cause damage on the human, there is no good for environment protection.
China Patent No. 200510018925.X provides a method for producing analytically pure sulfuric acid, which use the sulfur trioxide gas as raw material, make the sulfur trioxide react with the water to get analytically pure sulfuric acid. Although this method reduces the energy consumption, the content of impurities level of the product is too high to be in conformity with the requirements of SEMI C12 standard.
Currently, there is no report on the manufacture method of the ultra-pure sulfuric acid which is in conformity with SEMI C12 standard in domestic range.